1. Technical Field
The present disclosure refers to an integrated programmable gain amplifier circuit and to a system including such an integrated circuit.
2. Description of the Related Art
With reference to the block diagram shown in FIG. 1, transmission and recording systems 1 are known in the field of mobile telephony voice/audio for receiving at input a microphone analog signal in order to convert it into a digital signal. The system includes an integrated circuit in which a programmable gain amplifier 2 (which in this configuration is commonly called pre-amplifier), an anti-aliasing filter 3, and an analog-digital converter 4 are provided.
In such transmission or recording systems 1, the pre-amplifier 2 is of the programmable gain type, in order to adapt the dynamics of the microphone signal, depending on the particular type of microphone used, to the input dynamic of the analog-digital converter 4. The gain of the pre-amplifier 2 is set during system setup in order to provide the best performing interfacing of the analog-digital converter 4 to the particular microphone model to be used in the system.
The anti-aliasing filter 3 has the task of eliminating the spurious components of the input microphone signal that surround the sampling frequency of the analog-digital converter in order to avoid these components from being carried in the band used by the sampling operation. Such a filter 3 is therefore a low pass filter.
The analog-digital converter 4 is provided for converting the preamplified and filtered analog microphone signal into a digital signal, for example in order to store or transmit this digital signal.
In designing next-generation mobile communications devices, such as cellular telephone devices, for which audio performances will be required, which may be similar to those of consumer hi-fi equipments, the need is felt for reducing the noise introduced in the digital samples by the path through the various blocks 2, 3, and 4 represented in the diagram of FIG. 1.
It has been observed that in order to achieve this goal, it is necessary to develop integrated circuits with an increase of consumption and surface area of the three blocks 2, 3 and 4 of FIG. 1, since the noise decreases with the square root of the these two parameters. However, this solution is not practical since, in order to achieve the required performances in terms of noise reduction, it would be necessary to design mobile communications devices with an unacceptable level of consumption, although it is known that the battery consumption is a very important performance factor, and it would be necessary to develop integrated circuits that are not competitive in terms of silicon area requirements.